The purpose of this project is to determine the chemical nature of the catalytically active centers of glyceraldehyde 3-phosphate dehydrogenase and to relate these structures to the various activities of the enzyme in vivo and in vitro. Six types of reactions are catalyzed by the enzyme; dehydrogenase, transacetylase, phosphatease, esterase, diaphorase, and transphosphorylase. We propose to prepare enzyme complexes with substrates, coenzymes, and inhibitors in order to examine the catalytic mechanisms using electron paramagnetic resonance techniques. These studies will be correlated with the more detailed crystallographic analyses of other laboratories. The data on the structure and catalytic mechanism will be extrapolated to an investigation of the functioning of the enzyme in the muscle cell. For example, this dehydrogenase is inhibited by ATP, phosphocreatine and intermediates of the glycolytic pathway. The mechanism of these inhibitions and their relationship to contraction and relaxation will be further investigated. An attempt will be made to relate the findings to the metabolic disorders of muscular dystrophy.